From the time of its commerical introduction, Triclosan has been produced by a process consisting of the diazotization of 2,4,4'-trichloro-2'-aminodiphenyl ether with nitrosylsulfuric acid, followed by hydrolysis of the resulting diazonium bisulfate with hot, strong sulfuric acid. It is a disagreeable and wasteful aspect of this process that there is generated thereby a very substantial amount of an offensive co-product, 2,4,8-trichlorodibenzofuran. As a consequence it is necessary to separate this co-product from the formed Triclosan and to protect the environment by destroying it e.g., by incineration. Also, lengthy, expensive and rigorous purification procedures are needed to reduce the amount of this possibly hazardous substance to tolerable levels in Triclosan.
It is a practical objective therefore to produce Triclosan by a synthesis which does not generate 2,4,8-trichlorodibenzofuran as a co-product. Such a process has been described whereby Triclosan is formed by treating 2,4,4'-trichloro-2'-methoxydiphenyl ether with anhydrous aluminum chloride, or with hydrobromic acid. This precursor to Triclosan has required the availability of 4-chloro-2-methoxyphenol (4-chloroguaiacol), the preparation of which is cumbersome and expensive. The chlorination of guaiacol (2-methoxyphenol) generates large amounts of acidic wastes. Moreover it produces, along with the desired compound, several other chlorinated products which must be removed by meticulous fractional distillation in vacuum.